From help-octave-request at bevo dot che dot wisc dot edu  Fri Feb  4 05:01:32 2000
Subject: Re: same mem problem
From: "Erich Schneider" <eschneider at nefo dot med dot uni-muenchen dot de>
To: "help-octave at bevo dot che dot wisc dot edu" <help-octave@bevo.che.wisc.edu>,         "Guest9" <Guest9@gns.cri.nz>
Date: Fri, 04 Feb 00 12:11:49 

Try this code and watch the memory usage:

clear;
f5hs3=rand(570,720)*5000;
f5ls3=rand(570,720)*5000+1;
C=-636.73*(f5hs3-f5ls3)./f5ls3-0.079098*f5hs3+332.15;
clear f5ls3;
[m,n]=size(f5hs3);
C_temp1=C(2:2:m,2:2:n);
clear C;
C_temp=C_temp1(:);
clear C_temp1;
average=mean(C_temp(find(f5hs3(2:2:m,2:2:n)<3400)))
clear C_temp;

You could even subdivide the calculation for C into something like:

c1 = f5hs3-f5ls3;
c2 = -636.73.*c1./f5ls3;
clear c1;
C = c2+332.15-0.079098.*f5hs3;
clear c2;

I'm using 2.0.13, too, but couldn't reproduce your error when running
your script repeatedly. It seems to me that for the calculation of C
octave is storing 2 additional temporary matrices. Maybe subdividing
this and clearing the accessible matrices cX helps. I recommend the
step C_temp=C_temp1(:); clear C_temp1; because I saw the following
behaviour of octave 2.0.13 and .14:

a=ones(8000000,1);
a=ones(8000000,1);
memory exhausted bla ...
b=ones(4000000,1);
c=ones(4000000,1);

If memory is exhausted then why can I execute the steps for b and c?

I don't know whether this is a bug worth reporting or just a limitation
based on how octave internally uses memory. However, I speculate that
your problem rather seems to be related to the use of cygwin because I
couldn't reproduce your error. On Linux, "clear" definitely frees the
used memory and swap space.

On Fri, 4 Feb 2000 12:26:56 +1300, Guest9 wrote:

>
>
>Thanks Erich...it's running alot faster now; about 3 seconds for the calculation
>as opposed to something like 12.  Still now all that it means is that I get the
>same memory problem again, just quicker.  I've looked at task manager to see
>what's happening as I went through the script line by line:-
>
>mem usage for octave
>
>2480 Kb             start
>5856           loaded first matrix - size 570x720  so this is ok  570x720x8 is
>about 3200 K
>9064           second matrix - ok
>18768               calculated C -- so 570x720x24 = about 9600 K?  Why 24 bytes
>now?    (forgive my ignorance)
>18832               rest of minor calculations
>
>Ok, so apart from not understanding why it's 24, I can run the script through
>once fine.  When I try and run it a second time (after 'clear') it runs out of
>memory.  I was looking at a past help message that was similar to this and so
>ran through the script lines a second time.  After clear the mem usage stayed at
>the 18832 Kb and didn't increase when I loaded the two matrices again, it was
>trying to get C that it bombed.  So what I'm asking is how can I actually
>_clear_ the memory octave is using to run the script through again?

----------------------------------------------------------------------
Erich Schneider, Dipl.-Phys.     | eschneider at nefo dot med dot uni-muenchen dot de
Neurologische Forschung          | u7x31ay at lrz-muenchen dot de
Ludwig-Maximilians-Universit"at  | 
Klinikum Grosshadern, M"unchen   | Fax: +49,89,70906,101



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